JP2002313268A - Rotating cathode x-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotating anode X-ray tube that can made the distribution of potential stabilize and suppress the discharge of the X-ray tube glass bulb that is positioned at the vicinity of the X-ray radiation window of the tube container. SOLUTION: The X-ray tube 1 is installed on an anode-holding part 7 and a cathode-holding part 6 inside the tube container 12, in which insulating oil 15 is filled and a protective lead 5 in lined. X-rays are generated by rotating at a high speed the rotating anode 14 in the rotating magnetic field by a stator 2 and impressing high voltage on the X-ray tube 1 from the cable receptacles 4, and then by emitting electrons from the cathode 13, which is opposed to the target 14a and making collision with a target 14a. The radiated X-rays are irradiated to the outside from the X-ray radiation window 3, in which a metallic mask 9 of grounding potential is arranged on the inner side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotating anode X-ray tube apparatus in which a rotating anode X-ray tube using a glass X-ray tube envelope is sealed in insulating oil of a tube container. It relates to the stability of the potential distribution of the rotating anode X-ray tube with respect to the structure of the tube container.

[0002]

2. Description of the Related Art The structure of a conventional rotary anode X-ray tube apparatus is shown in FIG.
Shown in X-ray tube 1 having glass X-ray tube envelope 10
Is held by the anode holding part 7 and the cathode holding part 6 provided in the tube container 12 in which the insulating oil 15 is sealed. The rotating anode 14 is formed by integrating a tungsten umbrella-shaped target 14a and a rotor, and rotates at a high speed while being supported by a bearing of a fixed portion on the anode side. The cathode 13 is held by a cylinder, and its position is off the tube axis, and is composed of a focusing electrode and a tungsten filament. The rotating anode 14 is rotated at a high speed by an induction rotating magnetic field of a motor coil of the stator 2 provided on the anode side in the tube container 12. The electron impact area of the tungsten disk target 14a increases by rotation, and the input per unit area of the focal point increases. In many cases, a ball bearing is used in a vacuum in a rotating mechanism, held in a bearing case, and a thin film of lead, silver, or the like is used as a lubricant. The glass bulb of the X-ray envelope 10 is often made of hard glass. In order to make the inside of the X-ray envelope 10 high-vacuum, a glass thin chip tube from the end face side of the X-ray envelope 10 on the cathode side is used. After the evacuation, the tip tube is fused and sealed off. A protective lead 5 is lined inside the tube container 12 to prevent leakage of X-rays. Further, since the internal temperature rises due to the operation of the X-ray tube 1 and the volume of the insulating oil 15 expands, the bellows 8 is provided on the cathode side.

[0003] The X-ray tube 1 is housed in a tube container 12 in which an insulating oil 15 is sealed. In operation, a negative high voltage and a filament current are supplied from a cable receptacle 4 provided on both sides of the tube container 12 to a cathode. At 13, a positive high voltage is supplied to the rotating anode 14 from the outside. Then, the electron flow emitted from the filament of the cathode 13 is focused by the focusing electrode, and impacts on the surface of the umbrella-shaped target 14a of the tungsten disk of the rotating anode 14 rotating at high speed. At that time,
X-rays are radiated from the surface of the impacted tungsten disk, penetrate through the glass wall of the X-ray tube envelope 10 and the insulating oil 15, and are provided with an insulating material such as a resin provided at the X-ray radiation port of the tube container 12. X-ray emission window 3a made of

[0004]

The conventional rotary anode X-ray tube apparatus is constructed as described above. However, when X-ray fluoroscopy and imaging are repeated, the energy generated by the collision of the electron stream with the anode becomes large. Since the portion is converted into heat, the tungsten disk of the target 14a of the rotating anode 14 becomes hot. Part of the heat is generated by the anode holding portion 7 of the rotating anode 14.
Most of the heat is radiated from the tungsten disk and is directed to the cathode 13, through the glass bulb of the X-ray envelope 10, to the insulating oil 1 of the tube 12.
5 and the direction of the stator 2. Therefore, the temperature of the focusing electrode and the filament of the cathode 13 becomes high. Further, in order to emit electrons from the filament toward the target 14a of the rotary anode 14, a current is applied to the filament and heating is performed. Usually, the operating temperature is about 2500 ° K and the life is about 10,000 hours. However, the maximum available emission at this temperature is 0.5 A / cm ² . Life is determined by the evaporation of tungsten. When the diameter reaches the first 90%, thereafter, the temperature rises at an accelerated rate, and the rate of evaporation further increases, causing rapid fusing. If the degree of vacuum of the X-ray tube 1 is low and is about 10 ⁻⁵ to 10 ⁻⁴ mmHg or less, the evaporation of tungsten is accelerated by the oxidizing action of residual gas and ion bombardment, and the life is shortened. The evaporated tungsten adheres to the inner wall of the glass bulb of the X-ray tube envelope 10 having a relatively low temperature as a W scattering film. On the other hand, the cathode 13 is located near the asymmetrical X-ray emission window 3a supplied with a negative high voltage, the target 14a of the rotating anode 14 supplied with a positive high voltage, and the protective lead 5 is maintained at the ground potential. The inner and outer surfaces of a glass bulb, which is an X-ray tube envelope 10 located in the middle of a tube container 12 provided with an X-ray emission window 3a made of an insulating resin,
Positive and negative charges are charged up. Since the X-ray emission window 3a, which is an insulator, is present nearby, the above-mentioned W scattering film is added to the glass bulb around the X-ray emission window 3a in the X-ray tube envelope 10 of the X-ray tube 1. The inner and outer surfaces of the device are in a very unstable potential state. When such an unstable potential distribution state exists, discharge occurs between the cathode 13 and the target 14a of the rotating anode 14 via the inner surface of the glass bulb, or between the tube vessel 12 at the earth potential via the glass bulb. The glass bulb is destroyed by discharging, and the W scattering film becomes a floating potential and accumulates electric charge to induce discharge. There is a problem that the induced discharge causes ions of the residual gas to strike the surface of the filament, further evaporating tungsten from the filament, and further reducing the life of the filament.

The present invention has been made in view of such circumstances, and has been made to stabilize the potential distribution of an X-ray tube glass bulb located near an X-ray emission window of a tube container and suppress discharge. It is an object of the present invention to provide a rotating anode X-ray tube device capable of performing the above-mentioned steps.

[0006]

In order to achieve the above object, a rotary anode X-ray tube apparatus according to the present invention is held in an insulating oil inside a tube container by an anode holding portion and a cathode holding portion. A high-speed rotating umbrella-shaped anode, and a rotating anode X-ray tube in which a cathode is arranged oppositely in a high vacuum of the X-ray tube envelope. In a rotary anode X-ray tube apparatus for irradiating an X-ray emission window provided in a tube container to the outside, a ground potential member is arranged inside the X-ray emission window.

Further, the rotating anode X-ray tube apparatus of the present invention is held in an insulating oil inside a tube container by an anode holding portion and a cathode holding portion, and is used in a high vacuum of an X-ray tube envelope made of an insulating material. ,
A rotating anode X-ray tube in which a high-speed rotating umbrella-shaped anode and a cathode are arranged to face each other;
In a rotating anode X-ray tube apparatus for irradiating a line to the outside from an X-ray emission window provided in the tube container, a conductive paint is applied to the inside of the X-ray emission window to set a ground potential.

The rotary anode X-ray tube apparatus of the present invention is configured as described above, and an X-ray emission window provided in a tube container for irradiating X-rays emitted from the rotary anode X-ray tube to the outside. A ground potential member is arranged inside the inside of the device or a ground potential is obtained by applying a conductive paint.
As a result, the X-ray tube envelope of the X-ray tube is uniformly covered with the tube vessel set to the ground potential via the insulating oil, and the X-ray tube envelope near the X-ray emission window is opened. A stable potential distribution can be formed on the inner and outer surfaces of the glass bulb. X
By forming the ground potential surface in the radiation window portion, the potential distribution particularly on the inner surface of the X-ray tube envelope is stabilized, and the occurrence of minute discharge and further large discharge can be suppressed. Thereby, the life of the X-ray tube can be extended.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a rotary anode X-ray tube apparatus according to the present invention will be described with reference to FIGS. FIG.
FIG. 2 is a view showing a cross section of an embodiment in which a metal mask 9 is provided inside the X-ray emission window 3 of the rotary anode X-ray tube device. FIG. It is a figure showing the section of other examples of the present invention which applied conductive paint 11 inside. The rotating anode X-ray tube apparatus is arranged at one end of the X-ray tube envelope 10 made of hard glass evacuated to a high vacuum, and is rotated at a high speed by a rotating magnetic field of the stator 2. A rotating anode 14 having a target 14a,
The X-ray tube 1 composed of the X-ray tube envelope 10, the rotating anode 14 and the cathode 13 is connected to the anode holding unit 7 and the cathode 13, which emit the electrons by the filament and the focusing electrode arranged opposite thereto. A tube container 12 held by the holding portion 6 and sealed in the insulating oil 15 and lined with protective lead 5 on the inner wall;
A gable receptacle 4 for supplying a positive high voltage to the rotating anode 14 and simultaneously supplying a negative high voltage to the cathode 13 and a current to the filament, and electrons from the cathode 13 collide with the target 14a to emit X-rays. An X-ray radiation window 3 made of a resin and having a mask 9 or a conductive paint 11 provided inside the tube container 12 for irradiating X-rays to the outside and having a ground potential inside, and the insulating oil 15 expanded due to a rise in temperature inside. Sometimes, the bellows 8 adjusts the volume.

In the X-ray tube 1, a rotating anode 14 is formed by integrating a tungsten umbrella-shaped target 14 a and a rotating part, and is rotated at high speed by being supported by a bearing of a fixed part, and a cathode 13 is held by a cylinder. The position is deviated from the tube axis, and is constituted by a focusing electrode and a tungsten filament. A current voltage is supplied from the cable receptacle 4. X-ray tube envelope 1
Numeral 0 is made of hard glass or ceramic, and the inside thereof is evacuated to a high vacuum by a chip tube provided on the cathode side, and after the evacuation, the chip tube is fused and sealed off. The rotating anode 14 is applied with a high positive voltage from the cable receptacle 4 and rotates at high speed in a high vacuum by the rotating magnetic field of the motor coil of the stator 2 provided in the insulating oil 15. An umbrella-shaped tungsten or the like is used for the target 14a, and a ball bearing is used as a bearing for the rotating mechanism. The cathode 13 is held by a cylinder, its position is deviated from the tube axis, and a high negative voltage is applied from the cable receptacle 4 and at the same time current is supplied to the filament. Tungsten is used for the filament, supported by molybdenum anchors, one side is insulated by an insulator, and one is attached to a focusing electrode. The tube container 12 has an insulating oil 15 sealed therein and an anode holding portion 7 and a cathode holding portion 6 provided inside.
The tube 1 is held. Then, the rotating part of the rotary anode 14 is set at a position corresponding to the stator 2, and at the same time, the X-ray emission direction is set so as to correspond to the X-ray emission window 3. Then, a lead wire from the cable receptacle 4 is connected to the rotating anode 14 and the cathode 13. During operation, the temperature inside rises and the volume of the insulating oil 15 expands, so the bellows 8 is provided on the end face of the tube container 12.

The X-ray emission window 3 is provided in the tube container 12 for irradiating X-rays to the outside, and has resistance to X-rays.
This is a resin window with good X-ray transparency. The X-ray irradiation window 3 of the rotary anode X-ray tube apparatus according to the present invention has a mask 9 or a conductive paint 11 having a ground potential inside. The X-ray tube envelope 10 of the conventional rotary anode X-ray tube device is made of hard glass, and the X-ray emission window 3a is made of a resin having good X-ray resistance. It has insulation properties so as to withstand a voltage. However, in such a configuration, the potential distribution on the inner surface of the X-ray tube envelope 10 tends to be extremely unstable at the moment when a high voltage is applied to the X-ray tube 1. This is because it takes at least several milliseconds for charges to accumulate not only in the X-ray tube envelope 10 but also in the X-ray emission window 3a and stabilize. Such a fluid potential distribution leads to a minute discharge, which further facilitates the generation of a large discharge. On the other hand, the present rotary anode X-ray tube apparatus is shown in FIG.
As shown in FIG. 1 (B) which shows an enlarged view of a main part W of (A), a mask 9 is arranged inside the X-ray emission window 3. The mask 9 is made of a conductive material and is set to a ground potential. Lead and aluminum are used as preferred materials. The X-ray radiation window 3 itself is desirably made of resin in consideration of X-ray transmission. Conventionally, it has been considered that the X-ray emission window 3a needs to withstand a voltage. However, by providing the X-ray emission window 3 with a ground potential as described above, the X-ray emission window 3 itself does not require electrical insulation. However, there is no problem even if the X-ray emission window 3 is made of metal as in the embodiment. In this embodiment, the potential distribution in the portion of the X-ray emission window 3 and in the vicinity of the X-ray emission window 3 of the X-ray envelope 10 is easily constant and stable. Thus, it is possible to prevent a minute discharge on the inner surface of the X-ray tube envelope 10 and a large discharge accompanying the discharge. In the embodiment of FIG.
As shown in FIG. 2 (B) which shows an enlarged view of a main part W in FIG. 2 (A), the ground potential surface is formed of conductive paint 11 instead of metal.

Next, the operation of the rotary anode X-ray tube device will be described. First, a current is supplied to the electromagnetic coil of the stator 2 to rotate the rotating anode 14 at high speed, and a heating current is supplied to the filament of the cathode 13. Then, the high voltage generator is controlled by the X-ray controller to apply a negative high voltage to the cathode 13 and a positive high voltage to the rotating anode 14. At this time, the capacitance between the cathode 13 of the X-ray tube 1 and the rotating anode 14 and the distance between the cathode 13 and the tube vessel 12 at the ground potential and between the rotating anode 14 and the vessel 12 Since the glass insulator of the envelope 10 and the insulating oil 15 are present and the capacitance is present, at the time of the initial rise of the voltage, the waveform thereof is instantaneously changed to the charge corresponding to the aforementioned capacitance at the moment when the high voltage is applied. The waveform becomes distorted depending on the minute. Then, when thermoelectrons fly out of the cathode 13 and collide with the target 14a of the rotating anode 14, X
It generates rays, but also secondary electrons and reflected electrons. The secondary electrons and reflected electrons are returned to the target 14 again.
Although some of them collide with a, a part of them is charged up on the inner wall of the X-ray tube envelope 10. With respect to the charge, a charge having a positive charge is induced on the outer surface of the X-ray tube envelope 10. In this embodiment, since the mask 9 or the conductive paint 11 for forming the ground potential is provided inside the X-ray emission window 3, the electric charge charged up on the inner wall of the X-ray tube envelope 10 is stably maintained. Standing. If only the conventional X-ray radiation window 3a made of resin is used, the charge floats and moves on the inner wall of the X-ray envelope 10 in an unstable state, and spatters on the inner wall of the X-ray envelope 10. The tungsten scattering film of the filament is also added to become a floating potential, and accumulates electric charge to induce discharge. The induced discharge caused residual gas ions to strike the surface of the filament, further evaporating tungsten from the filament and further reducing the life of the filament. Further, the electric field intensity around the periphery changes every moment, and the disappearance and generation of the electric charge are repeated, so that a small discharge is generated, thereby inducing a large discharge and causing the X-ray tube 1 to fail. In the present invention, since the electric charge on the inner wall of the X-ray tube envelope 10 is fixed by the external uniform earth potential, the X-ray tube 1 can be operated stably.

[0013]

The rotary anode X-ray tube apparatus of the present invention is constructed as described above, and a ground potential member is arranged inside an X-ray emission window provided in a tube container of the rotary anode X-ray tube. Or, since the conductive paint is applied, the X-ray tube is uniformly shielded by a tube container set to the ground potential via insulating oil, and the inside and outside surfaces of the glass bulb of the X-ray tube near the X-ray emission window Then, a potential distribution of the stationary charges is formed. Therefore, X
The electric potential distribution on the inner surface of the tube glass bulb is stabilized, the generation of minute discharge and further large discharge can be suppressed, and the life of the X-ray tube can be extended.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a rotary anode X-ray tube apparatus of the present invention.

FIG. 2 is a view showing another embodiment of the rotary anode X-ray tube apparatus of the present invention.

FIG. 3 is a view showing a conventional rotary anode X-ray tube device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... X-ray tube 2 ... Stator 3, 3a ... X-ray radiation window 4 ... Cable receptacle 5 ... Protective lead 6 ... Cathode holding part 7 ... Anode holding part 8 ... Bellows 9 ... Mask 10 ... X-ray tube envelope 11 ... Conductive paint 12 ... Tube container 13 ... Cathode 14 ... Rotating anode 14a ... Target 15 ... Insulating oil

Claims (2)

[Claims] An umbrella-shaped anode which is held in an insulating oil inside a tube container by an anode holder and a cathode holder and rotates at a high speed in a high vacuum of an X-ray tube envelope made of an insulator; And a rotating anode X-ray tube device arranged to oppose the rotating anode X-ray tube, and irradiating an X-ray radiated from the rotating anode X-ray tube to the outside from an X-ray emission window provided in the tube container. A rotating anode X-ray tube device, wherein a ground potential member is arranged inside the X-ray emission window. 2. An umbrella-shaped anode which is held in an insulating oil inside a tube container by an anode holding portion and a cathode holding portion and rotates at a high speed in a high vacuum of an X-ray tube envelope made of an insulating material; And a rotating anode X-ray tube device arranged to oppose the rotating anode X-ray tube, and irradiating an X-ray radiated from the rotating anode X-ray tube to the outside from an X-ray emission window provided in the tube container. A rotating anode X-ray tube apparatus characterized in that a conductive paint is applied to the inside of the X-ray emission window to set a ground potential.